Coronary artery disease is a condition that causes narrowing of the coronary arteries, reducing blood flow to the heart muscle. Severe cases can result in a heart attack. A common treatment for coronary artery disease involves balloon angioplasty with or without stenting.
Angioplasty is a medical procedure in which a balloon is used to open these narrowed or blocked blood vessels of the heart. A catheter with a deflated balloon on its tip is passed into the narrowed artery segment, the balloon is inflated and the narrowed segment widened. Then the balloon is deflated and the catheter is removed. This is also known as Percutaneous Transluminal Coronary Angioplasty (PTCA).
About one-third of patients who undergo PTCA have restenosis of the widened segment within about six months of the procedure. In order to prevent restenosis, a metallic stent is commonly placed at the site of angioplasty (stenting). A stent is a metallic wire mesh tube that helps to keep open an artery after it is widened using angioplasty. Some of these stents are coated with a medication that is released locally into the arterial wall to further reduce the chances of arterial narrowing. These stents are called drug-eluting stents (DES), and are the most common variety of stents currently used. Examples of such medications include paclitaxel (TAXOL®) and other taxane derivatives, Biolimus A7, BIOLIMUS A9™, everolimus, sirolimus (rapamycin), pimecrolimus, or any other members of the -olimus family. Desirably, the medication is released within the body at a reproducible and predictable fashion so as to optimize the benefit of the medication to the patient over the desired period of time.
Approximately one million coronary stent procedures are performed annually in the United States. Once implanted into the heart artery, the inner lining of the artery grows over the metallic stent struts by a process called endothelialization. Through endothelialization the stent eventually becomes a part of the vessel wall.
A rare but potentially fatal complication associated with implantation of a DES in the coronary artery is the formation of a blood clot (thrombus) inside the blood vessel at the stented site. This can happen months or even years after the procedure, and is called “late stent thrombosis” (LST). LST is a vexing clinical problem (see W. H. Maisel, “Unanswered Questions—Drug-eluting Stents and the Risk of Late Thrombosis”, New England Journal of Medicine, vol. 356, page 981-984 (2007)), and is associated with high rates of heart attack and death.
Understanding its pathogenesis and its prevention, therefore, is of primary importance to management of patients with coronary artery disease. Delayed or late stent thrombosis is related to delayed endothelialization of the intra-coronary stent (see A. V. Finn, M. Joner, G. Nakazawa, et al., “Pathological Correlates of Late Drug-Eluting Stent Thrombosis: Strut Coverage as a Marker of Endothelialization”. Circulation Vol. 115, page 1-7 (2007). Needed in the art are devices, systems and methods to detect and monitor endothelialization of intravascular stent devices.